I don't think Siah for
Josiah or Trick for
Patrick are hipster. They just seem extremely artificial and gimmicky... like the kinds of things guys might call each other jokingly, almost trash-talk. Not like the kinds of short names people'd seriously introduce themselves with.
Shad for
Shadrach seems really obvious, although the name
Shadrach itself seems pretty "hipster."
Jojo also seems very ordinary as a nick, and so does
Sky.
Faukson does shorten naturally to
Fox. If Faukson was the person's first name, I'd suspect that it was coined just to get
Fox, though. So it seems artificial in a way. Deck for Decker seems natural enough, but Decker is very trendy style, not what I'd call hipster.